1976 Dart Overheating and other issues

I just shut it down and there is an ever so slight bubbling at the upper outlet in the metal just before the rubber hose. Barley noticeable, but probably a pinhole. Also, when I turn the key to ACC position to look at the gauge, the temp went from the lower tick to the middle after shutdown, but I assume that’s normal due to the reduced airflow from the fan since I shut it down.